It is well known in the United States, at least, that the formation of ice dams and icicles on the roofs of homes and other small buildings in winter weather is responsible for an excessive amount of damage to the homes, buildings and even the contents therein. The causes of ice damming and icicles are also well known, namely that when accumulated snow on a sloped roof top is caused to melt while ambient outdoor air temperatures are at or below the freezing temperature of water, or drop to such temperatures, the melt run-off flows downwardly on the sloped roof until it reaches an area of colder temperature, that is, sufficiently colder than the melt run-off is causing it to re-freeze, which normally occurs along the lower edge of the roof line, and/or within gutters and downspouts. Even though the ambient outdoor air temperature may not be warm enough to cause initial melting of such snow, such melting may nevertheless result due to other causes, such as from a rise in temperature within the unheated attic area of the home or building resulting from heat that escapes into the unheated attic area from the heated rooms therebelow. This rise in temperature can be more than insignificant as a snow covered roof acts as an excellent insulation to prevent heat loss through the snow covered roof.
While some older homes and buildings may have heated attics, present day home building practices usually provide an unheated attic, or at least an unheated air space between the top floor ceiling and the roof structure. Because such unheated attics and air spaces tend to become exceptionally cold in the wintertime, and exceptionally warm in the summertime, it is common practice to insulate the ceilings in the upper floors of the home or building from such unheated attics or air spaces, thereby insulating the living quarters from the outdoor air temperature, whether hot or cold. While the top floor ceiling is normally insulated, it is not normal practice to insulate the roof structure over the attic or air space. Thus, heat loss can normally be expected through the roof structure itself and while a snow cover will tend to insulate the attic air space, it does little to prevent heat loss into the roof structure itself. Accordingly, even though the attic air temperature may be only slightly above a freezing outdoor ambient air temperature, such a slight degree of warmth can be expected to warm the roof structure sufficiently to melt a considerable snow accumulation on the roof.
Normally, the melt run-off, as described above, will flow downwardly on a sloped roof under the snow cover until it reaches an area which is at or below the freezing temperature, such as roof surfaces not directly adjacent to the slightly warmed attic area, like the overhang area of the roof over the facia, and/or in gutters and downspouts, where the melt run-off then re-freezes to form ice. As the mass of such re-frozen run-off builds up, it can form what is commonly referred to as an "ice dam", which may form at the edge of the roof and tend to block the path of additional melt run-off. When ice dams form in gutters and downspouts, the gutters and downspouts can become blocked so that the run-off will overflow the edges of the gutters dripping downwardly to form icicles, which can accumulate and grow over time to very considerable sizes. It is of course well known that large icicles can present a significant danger to persons who must pass thereunder, not to mention damage to the gutters and downspouts themselves as a result of the weight of such icicles. In addition to the threat to personal safety and possible damage to gutters and downspouts, damage often results from the fact that the additional run-off, if so blocked at or near the edge of the roof by an ice dam, will tend to cause the blocked melt run-off to pool or back-up, seeping under the roof shingles and into the house or building so that the supporting wooden roof structure under the roof shingles not only becomes wet and water damaged, but the run-off can further seep or leak through the roof structure to cause water damage to the building walls and wall structures and even the building contents.
Unfortunately, traditional methods to alleviate the problems of ice dams and icicles are addressed primarily to treating the symptoms rather than the causes, in that home and building owners may often find themselves out-of-doors in cold winter weather knocking down icicles and/or chipping away ice dams. It is even more unfortunate that this effort itself often leads to damage to roof shingles, gutters and downspouts, with the very strong probability that the cycle will be repeated, with the ice dams and icicles reforming again.
One system that is available on the market to treat the causes of ice dams and icicles is the installation of one or more lengths of electrical heating cable which are usually installed in a zig-zag pattern adjacent to and along the lower edge of the roof. When properly installed, these heating cables are intended to heat at least certain roof areas to maintain one or more open molten water pathways along the edge of the roof thereby permitting molten run-off access to the gutters, to thereby prevent the formation of ice dams along the edge of the roof. To be completely effective, however, these electric heating cables should also be installed along the full width of the gutters and full length of the downspouts to a lever below grade, which unfortunately, is seldom the case.
In addition to the above discussed prior art concerning problems caused in winter weather, it is acknowledged that attic exhaust fans are well known which are used to overcome problems caused in hot summer weather. Such prior art attic fans normally include an electric motor driven fan adapted to exhaust exceptionally hot air from the attic of a home or building. Such exhaust fans are usually disposed at a high point of the attic ceiling, normally adjacent to a gable peak or apex between a pair of sloped roof surfaces. Such fans are generally mounted within a circular opening directly through the roof structure, such that the fan blade is aligned with and parallel to the roof, with the electric motor operatively connected to the fan blade, extending downwardly into the attic below the fan blades, and a "mushroom cap" type of cover secured to the roof directly over the fan blades to prevent the ingress of rain water and the like. A screen is also normally provided below the fan blades to prevent the ingress of insects and other unwanted solid debris. In the prior art, such exhaust fans have been solely utilized for the purposes of exhausting excessively hot attic air from the attic in summer weather to prevent heat conduction into ceiling surfaces therebelow, thereby assisting in efforts to keep the building cool with an air conditioning system. Indeed, despite the fact that the ceilings may be well insulated, such attic exhaust fans are well known to reduce electricity usage and bills by reducing air conditioner use.
Such attic fans of the prior art normally have a thermostatically controlled on-off switch which is adapted to turn the fan "on" when attic air reaches a temperature of 105.degree. F. to 115.degree. F. Even though the building ceiling is usually insulated against ambient air in the attic, it is known that, at least during exceptionally hot weather, enough heat is conducted through the insulated ceiling to warm such a ceiling and the air temperature in the upper rooms of the building, thereby reducing the effect of the air conditioning system in the building.